Passive coolers are utilized for cooling sensitive radiation detectors which are operative at cryogenic temperatures, the detectors being used to scan the earth from an orbit position about the earth. Applications for such detectors are in the weather satellites now in use and satellite Laser communication systems.
One particularly suitable passive cooler is described and disclosed in U.S. Pat. No. 3,817,320 assigned to the assignee of the present invention. The cooler described in this patent utilizes a suspension system described in U.S. Pat. No. 3,727,865 also assigned to the assignee of the present invention. The cooler described in U.S. Pat. No. 3,817,320 is of the type that is useful for sensors having medium resolution (i.e 0.6 mr instantaneous field of view). In this respect, the suspension system described in U.S. Pat. No. 3,727,865 is extremely suitable. However, a problem arises when utilizing a cooler in much higher resolution systems such as might be used in a geosynchronous orbit. In such an orbit, the satellite is positioned about 22,000 miles above the earth and would require sensors with 0.1 mr instantaneous field of view or less. At that resolution the optics used to collect the light from the earth and direct the light to the infra-red detector needs to have, as will be appreciated, a high degree of accuracy and stability. The same requirement would hold for very high performance sensors orbiting 500-1000 miles above the surface of the earth for use in earth resource observation applications. For this reason the suspension system required to mount the infra-red detector needs to be extremely precise and mechanically stable to cooperatively operate with such increased precision in optics. Thus a stiffer system is required to mount the infra-red detector than that disclosed in U.S. Pat. No 3,727,865.
However, such stiffer systems as utilized in the past include thermoplastic mounting insulators which exhibit creep and hysteresis. Such thermal mounts can be utilized to mount the outer stages or shields utilized in a passive cooler. Due to the precision alignment requirements of the optics and the infra-red detector, however, such prior art mounts are unsuitable for higher resolution sensors.